The present invention relates to expandable polymer compositions and uses thereof as foam-in-place reinforcement and/or insulation materials.
Polymeric foams are finding increasing application in the automotive industry. These foams are used for structural reinforcement, preventing corrosion and damping sound and vibration. In many cases, manufacturing is simplest and least expensive if the foam can be formed in place where it is needed, rather than assembling a previously-foamed part to the rest of the structure. For this reason, a variety of types of foamable compositions have been developed. These include formulations that are based on diverse polymers such as polyurethanes, epoxy resins and various ethylene copolymers. The formulation is inserted into a cavity where the foam is needed, and heated. The applied heat causes the formulation to expand and cure or crosslink to form a cellular structure.
In simple cases, the entire cavity is to be filled. Usually, accomplishing this is simply a matter of providing the cavity with enough of the expandable composition. In more complicated cases, only a portion of the cavity needs to be filled. For example, adequate sound and vibration dampening or corrosion protection may be achieved in some instances by filling only a portion of a cavity. It may be important in other cases to keep a portion of the cavity accessible for adjustment or repair purposes. In such cases, filling the entire cavity adds expense and weight but provides little additional benefit, and may even be detrimental.
Partial cavity filling is simple only in the case where the bottom portion of the cavity is to be filled. In that situation, the expandable composition can be inserted into the bottom of the cavity and allowed to foam upward to fill that portion of the cavity where the foam is needed. The amount of expandable composition that is added largely controls the extent to which the cavity is filled. By using more or less of the expandable composition, the cavity can be more or less filled.
The problem of partial cavity filling becomes much more difficult when the cavity has a complex shape, or when the bottommost portions of the cavity are to remain unfilled. The expandable compositions will tend to expand downwardly under the influence of gravity, and if supported from below tend to expand isotropically in all directions unless constrained in some manner. Therefore, it has been necessary to provide some mechanical means by which the expandable composition can be retained in the proper place in the cavity, and by which the direction of expansion can be controlled so only the desired portions of the cavity become filled with the expanded polymer. A variety of supports, baffles and dams have been used for that purpose. These all introduce complexity and cost, and often add unwanted weight.
What is desired is a simple, inexpensive method by which cavities can be partially filled with an expanded polymer composition.